1. Field of the Invention
The present invention relates to a resin multilayer substrate including at least two resin layers and via conductors, and a method for manufacturing the resin multilayer substrate.
2. Description of the Related Art
In recent years, with more electronic components being densely packed into packages, resin multilayer substrates have been used for mounting electronic components, in which via conductors in communication with each other are provided for respective multiple stacked resin layers provided with a plurality of via holes, with an increased density of conductive paste in a plurality of via holes. For example, Japanese Patent Application Laid-Open No. 2003-124380 discloses a resin multilayer substrate which has respective resin layers provided with via conductors in communication with each other, and a method for manufacturing the resin multilayer substrate.
In the case of an electronic component-containing module and a manufacturing method therefor as disclosed in Japanese Patent Application Laid-Open No. 2003-124380, a carrier with an IC mounted thereon is coated with an insulating layer composed of a thermosetting resin to provide a cured wiring substrate, and inner via holes are formed in the wiring substrate to form through via holes. Blind via holes and the through via holes are each filled with a conductive paste, and a thin resin layer is laminated onto the wiring substrate so as to provide the blind via holes and through via holes in communication with each other. Copper foil is laminated onto the thin resin layer, the thin resin layer and the conductive paste are brought into a cured state, and the copper foil is subjected to patterning to form surface electrodes.
However, in the case of the method for manufacturing a resin multilayer substrate as disclosed in Japanese Patent Application Laid-Open No. 2003-124380, it is not possible to fill more than the internal volume of the blind via holes and through via holes with the conductive paste. Thus, the method has a problem that it is not possible to increase the density of the conductive paste in the blind via holes and through via holes, or reduce the resistance value of blind via conductors and through via conductors obtained by curing the conductive paste in the blind via holes and through via holes.
In addition, the blind via holes and the through via holes are each filled with the conductive paste, and then, the thin resin layer is laminated onto the wiring substrate. Thus, the method has a problem that the conductive paste is exuded from the blind via holes or the through via holes to spread to the interface between the wiring substrate and the thin resin layer, thereby decreasing the insulation performance between the wiring substrate and the thin resin layer.
Furthermore, because the thin resin layer is small in thickness, the area of contact is small between the through via holes and the conductive paste filling the through via holes, and the method thus has a problem that there is a possibility that the force generated when the conductive paste is brought into a cured state peels off, from the thin resin layer, the surface electrodes formed on the through via holes, along with the conductive paste filling the through via holes.